JOLRNAL OF SCIENCE &TECHNOLOG> * No 83B-20I1 A NEW MAXIMUM POWER POINT TRACKING ALGORITHM IN PV SYSTEMS USING FRACTIONAL ESTIMATION GlAl THUAT M I X A C DjNH DIEM CONG SUAT CUC DAI TRONG HE THONG PV SU' DUNG PHUONG PHAP U'6C TINH PH.AN SO Phan Quoc Dzung, Nguyen Nhat Quang, Le Dinh Khoa, Nguyen Truong Dan Vu, Le Minh Phuong Ho Chi Minh City University of Technology ABSTRACT This paper presents an Improved algorithm of quick and accurate Maximum Power Point Tracking (MPPT) based on Incremental conductance algorithm, Fractional Open Circuit Voltage and Short Circuit Current The proposed algorithm estimates the short circuit current or open circuit voltage, then using Fractional Short Circuit Current or Fractional Open Circuit Voltage algorithm to quickly determine point close to MPP MPP will be accurately determined due to Incremental conductance algorithm The proposed algorithm can Identify quickly and correctly MPP when the environmental temperature and solar radiation change The results of prgposed algorithm are made by simulating with MATLAB/Simulink program and experimenting with kit dSPACE DS 1104 Keyword; Maximum power point tracking (MPPT), Incremental Conductance (Inc-cond), Fractional Open Circuit Voltage, Fractional Short Circuit Currenf Matlab/Simulink, dSPACE DS1104 TOM TAT Bii bio trinh biy mdt giii thuit di tiin xic dinh diim cdng suit cwc dai (Maximum Power Point Tracking - MPPT) mat cich nhanh chdng vi chinh xic dwa vio cic giii thuit Incremental Conductance, Fractional Open Circuit Voltage vi Fractional Short Circuit Current Giii thuit di xuk se xic dinh ddng dien ngin mach hoac dien ip hd mach, sau dd sir dung giii thuat Fractional Short Circuit Current hoic Fractional Open Circuit Voltage di nhanh chdng dwa vi diim gin MPP MPP se dwgc xic dinh chinh xic nhd vio giai thuat Incremental Conductance Giii thuat di xuit xic d/n/i nhanh chdng vi chinh xic MPP cd sw thay ddi cua diiu kien nhiet mdi trwdng vi birc xa m^t trdi Kit qui giii thuit di xuit dwgc thwc hien bing chwang trinh md phdng MATLAB/Simulink v^ thi/c nghiim Kit dSPACE DSl 104 ([7,9,10]) such as Perturb and observe (P & 0), Incremental conductance (IncCond), Fractional Open Circuit Voltage, Fractional Short Circuit current or ANN based algorithm ([6], [8])to determine MPPT P & O algorithm is offen used in practice because it's simple lo implement But this algorithm does not specify MPP exactly when there is rapid change ol solar radiation IncCond algorithm overcome the disadvantages of P & O but the respond time is not fast ANN is a method to determine MPP quicklv and accurately ANN algorithm would leam characteristics of a specific photovoltaic panels so when the photovoltaic system is changed, the algorithm must leam i new characteristic In the course of long-tem use the characteristics of photovoltaic panel wil be changed, resulting in inaccurate algorithm I INTRODUCTION When a photovoltaic (PV) system is connected to the load, the system will operate at the intersection of the I-V characteristic of the photovoltaic and the load characteristic To increase the effectiveness of photovoltaic svstem, the photovoltaic svstem should be operated at the maximum power point Maximum power point is not a fixed point vvhich depends on conditions of environmental temperature and solar radiation Natural environmental condition are verv volatile, so the MPPT controller for photovoltaic systems is verv essential The MPPT controller have an impact on the DC-DC converter to inject maximum power at the output before the sv stem is connected to the load or DC-AC converter for grid connection Many MPPT algorithms have been studied and developed 72 J U l K N \ L OF S C I E N C E * TECHNOLOGV * No 83B-2011 Improvements of MPPT algorithm have been researched and developed in [1-5.11] Reference [11] proposes a two-stage algorithm that offers fast tracking in the first stage and fine tracking in the second stage This method remains a problem of determining VQC (Open Circuit Voltage) left domain of the 1-V characteristic, there is an almost linear relationship between IMPP and Isc of the PV and the value of Isc is determined in the first calculation cycles ^Ii + sc ('2 - ' ) V2-V1 In which: IREF = This paper presents a new algorithm of MPPT based on improved IncCond algorithm combined with Fractional Short Circuit Current and Fractional Open Circuit Vohage algorithms This method will determine short circuit current if the photovoltaic system operates on the left of I-V characteristics or open circuit voltage if the system works on the right of I-V characteristics Then Fractional Short Circuit Current or Fractional Open Circuit Voltage algorithms will be implemented to put the power around the MPP quickly and then IncCond algorithm is used to determine the exact MPP The proposed algorithm not only identifies quickly and accurately the MPP, but also is not affected by the aging of the system in long term use (-V,) (1) K|*lsc (2) W here: K| is a constant chosen at random with constant K| = 0.75: 0.92 in Fractional Short Circuit Current algorithm In the next calculation cycles, the photovoltaic system will operate in the middle domain Incremental conductance algorithm is used to determine IREF so that it operates at MPP At the beginning, if the photovoltaic system operates in the right domain, the algorithm will determine MPP based on the correspondent value of VREF Assume that in the right domain of the 1-V characteristic, there is a near linear relationship between VMMP and VQC of the PV array and the value of VQC is determined in the first calculation cycles II THE NEW ALGORITHM The proposed algorithm divides I-V characteristics into three domains: the left, the middle and the right domain According to initial conditions of whether the photovoltaic svstem is operating in the left or right domain, the algorithm will detennine Isc or VQC Voc = V, + ( ^ ) ( - l , ) (3) In which: VREF = K2*Voc (4) Where: K2 is a constant chosen at random with constant K2 = 0.72: 0.78 in Fractional Open Circuit Voltage algorithm In the next calculation cycles, the photovoltaic system will operate in the middle domain Incremental conductance algorithm is used to determine ^ REF sO tuat it OpcfatCS 2l MPP MiUJIv dumnlnl ligiirel cell 1-V Characteristic When environmental conditions varv, the MPP will be changed by photovoltaic system, depending on the varience of current value at the point of change, the algorithm will determine MPP according to the value of IREF or \R£F.Its working principle can be explained using a flowchart show in Fig Let : of a pholovoltaic dl dV At the beginning, if the photovoltaic svsieni operates in the left domain, the algorithm will determine the MPP based on the correspondent value of IRIF Assume that in the (5) (6) Algorithm detennining IREF or VREF according to Ise or \ OC is shown in l''ig.3 73 JOI RNAL OF SCIENCE & TECHNOLOG\ ^U OJO - »u toolbox of SimPowerSv stems Components of the system include: PV An-av: 01 module PV SX 3200 Voc = 30.8 V, Isc = i.7 A (nonnal radiation); DC-DC Converter: Buck-Boost Converter vvitli parameters Ci = 2500pF L = 1.5 mH, C:=5000pF; Load : resistance load sense V I S II Case 1: This paper compares the results oflhe simulation algorithm proposed and traditional IncCond algorithm l:iJlRI|.i-\i,|| Irradiation and ambient temperature in the simulation are:T = 25°C and lamda kW/m2 The proposed method tracks to the MPP faster than the conventional IncCond algorithm The proposed algorithm (Fig.5) reach to the MPP in 0.02s but the IncCond algorthim (Fig.6) reach to the MPP in 0.2s inv MjzLirillim V ualcLilatcd iia'ordini; in III! I or Vm I * Keiucn ^ Figure Flowchart oflhe proposed algorithm '.' ll Voc SI-111 ' *• ~ > i \ , r > lref=0 lVirf=V I lref-0 j I.I-I \ref-0 \i.i V Irel-J Figure5 P (' Power Response Curve with the propsed algorithm Isc- Va licl K Ist Vref m l i Figiire6 PV Power Response Curve with Inc algorithm Case 2: •ibilily of the proposed algorithm lo reponse to the changes of the environmental temperature conditions Irradiance is constant with lamda = lkW/m2 Ambient temperature in the simulation are: • Time: t = 0s-0.3 s: T = 25°C • Time: t = 0.3s-0.55s: T = 35°C • Time: t = 0.55s-Is: f = 30"C Irel-l Vid « Figure Flowcharl algorithm determines Iiu.i or I 'nrr III SIMULATION The photovoltaic svstem model consists of PV artay the buck - boost converter, load R and MPPT controller m- '!' ,C \:fcfi P (' Power Figure Figure fi P-T Cim Response ('iirve wilh with icmperatic lemperalure changes changes using'' using the proposed proposed algorithn algorithm Figure Block diagram of MPPT controller Svsieni model of the proposed algorithm is developed on \1.\T1 AB'Siinulink and 74 JULK.>AL Oh s t 1ENCE& TECHNOLOGV * No.83B-2011 Case 3: ihllity of ihe proposed algorithm reponse to the changes of solar irradiation lo Ambient temperature is constant: - 25"C Irradiation in the simulation are: T • Time: t = s - s : lamda = I kW/m- • Time: t=0.4s-0.8s: lamda=0.2 kW/m" • Time: t=0.8s-l 2s: lamda=0.8 kW/m" —iinin mm mm mm mm m m mill inmmm imnuim Figure II Experimental Comparing with traditional algorithm, the proposed algorithm has faster response and higher accuracy.When the environmental temperature or radiation intensity change, the proposed algorithm gives rapid response and accurate results model )0 01 02 03 04 0.5 Time Isi Figure 12 PV Power Curve in case I Figure 13 I-V Curve in case Tiiiifui 1.S Figure PV Power C 'urve wilh irradiation changes using the proposed algorithm > 10 : :i) ;: Figure 10 P-V Curve with irradiation changes - using the proposed algorithm Figure 14 P-V Curve in case I I \ EXPERIMENT RESULT The proposed algorithm is implemented on the experimental Kit dSPACE DS 1104 to test the easibility of the algorithm Components oflhe svsieni include: PV Arrav: module PV H-Tech I \ \ \',H = 10.9 V, Isc = 1.2 A (radiation of lamp); DC-DC Converter: Buck-Boost Converter with parameters : C, = 3900pF, L = 1.5 mH, C; = 5()00pF; Load: resistance load; Controller MPPT: Kit dSPACE DSl 104 set on computer and can communicate with program \ l M l AH'Simuliiik Case 1: Proposed algorithm determine according lo I'/(/./ MPPT Information of photovoltaic svstem using proposed algorithm is demonstrated in Control Desk Proposed algorithm determine MPP according to VREF for 0.02s (Fig 12) The initial photovoltaic system operates at open circuit voltage and then immediately operates at maximum power point (Fig 13-14) Case Proposed algorithm determine according to Im / MPP Information of photovoltaic system using proposed algorithm is demonstrated in Control Desk Proposed algorithm determine MPIM according to IREF for 0.03s (Fig 15) The initial photovoltaic svstem operates at short circuit current and then immediately operates at maximum power point (Fig.16-17) JOLRNAL OF SCIENCE & TECHNOLOGY l.l ; )0 01 K iO 01 :'2 j i OJ ;••: j e o i ] :< C5 Co 0.7 * t Irr- Figure 15 PV Power Curve in case Figure 18 P'i'Power Curve in case Figure 16 I-V Curve in case s Votage (V) 10111; Figure 20 P-V Curve in case Figure 1' P-1' Curve in case Case 3: Traditional determine MPPT IncCond Figure 19 U Curve in case IV CONCLUSION algorithm The proposed algorithm satisfies the two essential elements in determining MPP, which are fast and accurate response in case of rapid change of environmental conditions of temperature and solar radiation, compared to traditional algorithms Information of photovoltaic system using IncCond algorithm is demonstrated in Control Desk IncCond algorithm determine MPPT according to VREF for 0.45s (Fig 18) The initial photovoltaic system operates at open circuit voltage and then step bv step operates at maximum power point (Fig 19-20) The proposed algorithm can determine MPP accurately bv both current and voltage When there is a change in ambient temperature or radiation intensity', the proposed algorithm has good response, even at low radiation intensity (light sun) The main utility of the algorithm: Not affected by the property of the photovoltaic; No additional photovoltaic system to determine the open circuit VQC or short circuit current lsc;Good response even when the solar irradiation is low; Identify MPPT by the current and voltage, the calculation algorithm can be implemented easily in the DSP microcontroller in the future REFERENCES A.J.Mahdi, \\ H.Tang and Q.H.Wu, "Improvement of a MPPT Algorithm for PV Systems and Its Experimental Validation"" International Conference on Renewable Energies and Power Quality Granada, 23 rd to 25 th March, 2010 Carlos A P Tavares Karia T F Leite, Water I Suemitsu, Maria D Bellar, Performance Evaluation of Photovoltaic Solar System with Different MPPT Methods", ICON 09, 35th Annual Conference of IEEE Industrial Electronics, p.719-724 C Liu, B Wu R Cheung "Advance Algorithm for MPPT Control of Photovoltaic Svslems" Canadian Solar Building Conference Montreal August 20-24 2004 C.Hua, C.Shen." Studv of Maximum Power Tracking Techniques and Control of DC/DC Converters for Photovoltaic Power System"" PESC98 Record.29th Annual Conferrence of IEEE Power Electronics Specialists,Vol.I,p.86-93 76 JOI RNAL OF SCIENCE & TECHNOLOGV * No 83B-2011 J.H.Lee, H.Bae, B.H.Cho, " Advanced Incremental Conductance MPPT Algorithm with a Variable Step Size"", EPE-PEMC 2006,12th Intemational Conference of IEEE Power Electronics and Motion Control, p.603-607 M.S.Kaiser, S.K.Aditva R.K.Mazumder, " Performance Evaluation of A Maximum power Point Tracker (MPPT) For Solar Electric Vehicle Using Artificial Neural Network" Daffodil Intemational University Joumal of Science and Technology, Volume 1, issuse 1, July 2006 M.A.S.Masoum, M.Sarvi, Voltage and Current Based MPPT of Solar Arrays under Variable Insolation and Temperature Conditions", Universities Power Engineering Conference, 2008 P.Q.Dung, LM.Phuong, H.H.Lee, L.D.Khoa, N.T.D.Vu, The New ANN Maximum Power Point Tracking Algorithm Using ANN- Based Solar PV Systems", Tencon2010, Fukuoka, Japanese T.Esram, P.L.Chapman,"Comparison of Photovoltaic Array Maximum Power Point Tracking Techniques", IEEE Transaction on Energy Conversion, Vol 22, No 2, June 2007 10 W.Xiao, W.G.Dunford, P.R.Palmer and Antoine Capel, Application of Centered Differentiation and Steepest Descent to Maximum Power Point Tracking"", IEEE Transactions on Industrial Electronics, Vol 54, No.5, October 2007 11 X.Wang and A.P.Hu, "An Improved Maximum Power Point Tracking Algorithms for Photovoltaic Systems", Australasian Universities Power Engineering Conference (AUPEC 2004), 26-29 September 2004, Bribane, Australia .liilhor 's address: Phan Quoc Dung - Tel: (+84)903.657.486; Email: Phan_quoc_dung(§yahoo.com Ho Chi Minh City Universitv of Technology No 268, Ly Thuong Kiet, Dist 10, Ho Chi Minh City ... TECHNOLOG\ ^U OJO - »u toolbox of SimPowerSv stems Components of the system include: PV An-av: 01 module PV SX 3200 Voc = 30.8 V, Isc = i.7 A (nonnal radiation); DC-DC Converter: Buck-Boost Converter... accurate results model )0 01 02 03 04 0.5 Time Isi Figure 12 PV Power Curve in case I Figure 13 I-V Curve in case Tiiiifui 1.S Figure PV Power C ''urve wilh irradiation changes using the proposed... dSPACE DS 1104 to test the easibility of the algorithm Components oflhe svsieni include: PV Arrav: module PV H-Tech I \ \ '',H = 10.9 V, Isc = 1.2 A (radiation of lamp); DC-DC Converter: Buck-Boost